Place 12 ounces of berries in a bowl, toss with ¼ cup of sugar and allow to sit for 15 minutes or until fruit exudes some juice. Mash with a potato masher or sturdy fork; you want to break them down but leave some texture. Chill well, at least 30 minutes or up to 4 hours.
Right before serving whip the cream with reserved 1 teaspoon sugar and the vanilla just until soft peaks form.
Fold the fruit and cream together, but not too thoroughly. You want there to be pretty pinkish-red streaks of fruit. Carefully spoon into goblets, garnish with extra slices of berries if using, and serve immediately.
Recipe by Bakepedia at https://www.bakepedia.com/strawberry-fool/